Segmented die holder for drawing apparatus



Nov. 17, 1970 J. w. HINSHAW 3,540,259

SEGMENTED DIE HOLDER FOR DRAWING APPARATUS Filed Aug. 20, 1968 3 Sheets-Sheet l INVEN Toe Jamv VV. Llwsmqw m ,1! i/m/ fi-rroewEvs.

Nov. 17, 1970 J. w. HINSHAW SEGMENTED DIE HOLDER FOR DRAWING APPARATUS Filed Aug. 20, 1968 3 Sheets-Sheet 2 IZIG. 5.

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SEGMENTED DIE HOLDER FOR DRAWING APPARATUS Filed Aug. 20, 1968 Y 3 Sheets-Sheet 3 ADJ USTABLE FLUID PREssuRE SOURCE SELECTOR MANIFOLD IN VEN roe (Io/0v m llx/vsunw mM/m/ IOTTOQNEVJ.

3,540,259 SEGMENTED DIE HOLDER FOR DRAWING APPARATUS John W. Hinshaw, Garden Grove, Calif., assignor to Battelle Development Corporation, Columbus, Ohio,

a corporation of Delaware Filed Aug. 20, 1968, Ser. No. 753,988 Int. Cl. BZlc 3/12 US. Cl. 72-465 18 Claims ABSTRACT OF THE DISCLOSURE A segmented die holder comprising a symmetrical annular array of three or more holder segments which support a drawing die ring of solid material coaxially therein. The segments are supported and guided for either collective or selective radial expansion and contraction between a pair of parallel plate surfaces arranged normal to the drawing axis, and serve to provide control of the effective working strength of the die ring relative to the workpiece, to reduce the amount of die ring material required, to reduce friction between die ring and seat, and to maintain proper die ring alignment.

BACKGROUND OF THE INVENTION Tube drawing, including such phases thereof as tube sinking, tube wall sizing, and tube tapering, is generally accomplished on a drawbench by drawing the tubing through a die ring of solid metal. In some types of tube drawing, as for example in tube tapering, this die ring must be variable as to its internal diameter, being either expansible or contractable, or both.

Such tube drawing involves the application of relatively large axial forces on the die ring, and accordingly a die seat must be provided on the drawbench which is capable of holding the die ring in alignment with the tubing and also capable of supporting the die ring against such axial forces. Typically, in the prior art such die ring seats were in the form of a rigid, heavy ring or plate for backing up the die, the ring or plate being apertured for passage of the tube therethrough after the tube passed through the die. Frequently such prior art solid, apertured die holders were counterbored at the forward face thereof for seating of the die in a fixed position relative to the die holder.

A problem encountered in the use of such solid die holders is that it was difiicult to accurately align the die with the workpiece so as to assure uniform deforma tion of the workpiece during the drawing operation. Any misalignment occurring between the die ring and the die holder, or between the die holder and the drawbench, results in imperfect centering of the die relative to the workpiece, with a consequent likelihood of improper deformation of the workpiece. With such prior art solid die seats, once the drawing operation is commenced and substantial axial forces are applied between the die ring and die holder, the friction between the die ring and holder precludes any substantial self-centering action, so that an off-center condition will usually remain during the entire drawing operation. Normally such drawing operations are accomplished on a horizontal drawbench, whereby the force of gravity on the die ring or die holder, or both, tends to establish an off-center initial condition.

The foregoing problems become much more severe, and additional problems arise, where the die ring is variable in size, as for example where the die ring is employed to draw a cylindrical tube into a tapered configuration over a tapered mandrel. In this case, the die ring must usually expand, or must sometimes contract, and such expansion or contraction is opposed and retarded by varynited States Patent Patented Nov. 17, 1970 ice ing amounts of frictional force between the die ring and the die holder seat, which results in an unpredictable amount of confining force of the die on the workpiece, and a further tendency toward misalignment between the die and the workpiece.

A major problem in the use of a variable die ring of solid material is in maintaining the strength of the die relative to the workpiece throughout the changing configurations required. The die must remain sufficiently strong to deform the workpiece, as required, but it must on the other hand be sufliciently weak to be deformed by the workpiece when a change in die configuration is required. The resistance of the die and of the workpiece to deformation will vary a great deal during the operation, yet the relative strengths must be maintained within certain ranges required to perform the specified deformations.

The operator has very little control over the strength and physical properties of the workpiece, as these are generally determined by the type of material in the workpiece, its past metallurgical history, and the shape to be achieved. Similarly, the operator has very little control over the strength and physical properties of the die during the deformation process. The operator can exercise a certain amount of control through the selection of die material and the preparation of the die; however, once the die begins to deform, the properties of the die are changed by cold working and a number of variables enter the picture which the operator cannot control. The conventional die holder in no way assists the operator to control the constricting force of the die as the physical properties of the die and workpiece, and hence the relative strengths thereof, vary during the drawing operation.

Another problem in connection with conventional support means for variable tube drawing dies is that such support means did not, except for the uncertain forces of friction discussed above, assist the die ring in its constrictive force on the tube being drawn. The result was that an undesirably large mass of die material frequently had to be employed to provide the required amount of constricting force for the particular tube drawing job. This resulted in undesirably large costs for the die material and for reforming the die material into a new die where possible, and resulted in increased effects of work hardening and consequent changes in the physical properties of the die material during the drawing operation.

A still further problem in connection with prior art drawing die supports is that they did not provide for the selective increase or decrease of radially inwardly directed supporting forces at different points around the periphery of the die, and accordingly permitted only minimum variations from round of the cross-sectional tube shapes that could be drawn thereby.

One prior art attempt to solve some of the foregoing problems is disclosed in my US. Pat. No. 3,327,513, issued June 27, 1967, for Method and Apparatus for Working Metal, wherein a die holder for a variable tube drawing die is shown which consists of a pair of semicircular holder segments within which the variable die is seated, the segments being biased toward each other by means of a spring loop disposed thereabout, and the segments being backed up by a solid end plate. While such two-segment die holder was expansible, it nevertheless failed to solve most of the foregoing problems because friction of these two segments against the solid backup plate prevented free expansion thereof, the expansion when it did occur was not uniform, the two segments sometimes opening up only at one side, and in general opening in an irregular manner, and the semicircular ID of the two-segment holder allowing expansion and contraction thereof only normal 3 to the plane of separation of the two semicircular segments, but not in the direction of such plane of separation.

SUMMARY OF THE INVENTION In view of these and other problems in the art, it is an object of the present invention to provide a holder for supporting a solid die ring employed for drawing tubing or other elongated members, the holder comprising a symmetrical annular array of generally wedgeshaped segments supporting the die ring coaxially therein, the segments being supported and guided for either collective or selective radial expansion and contraction so as to hold the die ring in correct axial alignment and back up the ring in the radial direction, while at the same time adjusting to variations in the diameter of the die ring.

Another object of the invention is to provide a segmented die holder of the character described which includes biasing means peripherally arranged about the annular array of die holder segments for collectively biasing the segments radially inwardly against the die ring so so as to provide a self-centering action whereby the die ring will at all times be firmly held in the holder segments during an entire drawing operation, while at the same time the die ring is allowed to automatically seek and adjust to a centered or axially aligned position with respect to the workpiece and drawbench.

Another object of the invention is to provide a segmented die holder of the character described which includes adjustable means for applying radially inwardly directed constricting force to the wedge-shaped die holder segmentes which supplements the constricting force of the die ring itself against the workpiece, thereby allowing the use of die rings containing a much smaller mass of metal than otherwise required, and providing the operator with a wide latitude of control over the overall effective constricting force of the die against the workpiece, allowing the operator to maintain the required effective strength of the die during an entire drawing operation despite changes which occur in the physical properties of both the die and the workpiece because of cold working and other factors.

Another object of the invention is to provide a segmented die holder of the character described which includes means for individually adjusting the radially inwardly directed constricting forces of the holder segments against the die ring, whereby by selectively increasing or decreasing the radially inwardly directed supporting forces at different points around the periphery of the die ring a wide variety of cross-sectional tube shapes can be drawn.

A still further object of the invention is to provide a segmented die holder of the character described which, by being expansible or contractable according to expansion and contraction of the die ring supported therein, greatly reduces or substantially eliminates the heretofore generally unpredictable and variable frictional forces between the die ring and die holder seat, thereby permitting more accurate alignment between the die and the workpiece, and more accurate operator control over the overall constricting force of the die against the workpiece.

Further objects and advantages of this invention will appear during the course of the following part of this specification, wherein the details of construction and mode of operation of several preferred embodiments are described with reference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an axial sectional view illustrating a first form of segmented die holder according to the present invention, with a solid die ring supported therein.

FIG. 2 is a fragmentary transverse section taken on the line 22 in FIG. 1.

FIG. 3 is a fragmentary transverse section taken on the line 33 in FIG. 1.

FIG. 4 is an enlarged perspective view illustrating one 4 of the die holder segments employed in the form of the invention shown in FIGS. 1 to 3.

FIG. 5 is an axial sectional view illustrating a second form of segmented die holder according to the invention, with pressure control means therefor diagrammatically illustrated.

FIG. 6 is a fragmentary transverse section taken on the line 66 in FIG. 5.

FIG. 7 is a fragmentary axial section, partly in elevation, illustrating a third form of segmented die holder according to the invention.

FIG. 8 is a fragmentary transverse section taken on the line 88 in FIG. 7.

FIG. 9 is an axial section, partly in elevation, illustrating a fourth form of segmented die holder according to the invention, with pressure control means therefor illustrated diagrammatically, the die and die holder being illustrated in FIG. 9 in partially expanded positions during the drawing of a tapered tube.

FIG. 10 is a fragmentary transverse section taken on the line 1010 in FIG. 9.

FIG. 11 is a fragmentary axial section illustrating a fifth form of segmented die holder according to the invention.

FIGURE 12 is a fragmentary transverse section taken on the line 1212 in FIGURE 11.

DETAILED DESCRIPTION Referring to the drawings, and at first to FIGS. 1 to 4 thereof, these figures illustratea first form of die holder according to the invention, which is generally designated 10. The die holder 10 includes a symmetrical annular array of generally wedge-shaped holder segments 12. At least three of the wedge-shaped segments 12 are employed, and preferably a larger number, since the greater the number of segments 12 that are employed the smaller the spacing between adjacent segments and the more complete the confining action of the segments on the die ring as the die ring expands. The die holder 10 shown in FIGS. 1 to 4 includes sixteen of the wedgeshaped segments 12, which has been found to be an adequate number of segments for most purposes.

Each of the wedge-shaped segments 12 has generally fiat, substantially parallel front and rear surfaces 14 and 16, respectively, and a pair of flat side surfaces 18 Which are substantially normal to the front and rear surfaces 14 and 16, the side surfaces 18 being located in planes which intersect at an included angle equal to 360 divided by the number of segments. Thus, the angle between the side surfaces 18 for each segment Where the minimum number of three segments is employed equals 360 divided by 3, or If sixteen of the segments 12 are employed as shown in the drawings, the included angle between side surfaces 18 will be 360 divided by 16 or 22 /2.

With the segments 12 in their fully constricted or closed relationship as illustrated in FIGS. 1 and 2, wherein adjacent side surfaces 18 of the segments are flush against each other, the segments 12 collectively define a generally continuous, closed annular inner surface of stepped configuration having forward and rearward cylindrical surface portions 20 and 22 separated by a forwardly facing annular shoulder 24 which serves as the die seat.

When the die segments 12 are thus in their constricted or closed relationship as shown in FIGS. 1 and 2, their outer or larger ends collectively define a generally cylindrical, continuous annular outer surface 25, the surface 25 having an annular groove centrally located therein which is of generally semicircular crosssection. A spring loop 28 is circumferentially engaged about the segments 12 and is seated in the annular groove 26, spring loop 28 comprising a spiral or helical type spring which is closed to a generally torus-shaped configuration.

Spring loop 28 is a tension spring which applies a constricting or closing force collectively against all of the segments 12.

Each of the segments 12 has a pair of generally hemispherical, radially spaced ball recesses 30 and 32 located in each of the sides 14 and 16 thereof. The ball recesses 30 and 32 are preferably substantially centered relative to a plane which bisects the angle included between the planes of the two side surfaces 18 of each segment 12.

FIGS. 1 and 2 illustrate a die ring of solid material supported coaxially within the annular array of die segments 12. The die ring 34 as illustrated in FIGS. 1 and 2 is in its initial, unexpanded condition, and in such condition its outer cylindrical surface 36 has a diameter which is substantially equal to the closed diameter of the forward inner surface portion 20 collectively defined by the holder segments 12. Die ring 34 also includes a curved, forwardly flaring inner working surface 38 extending from leading edge 40 to a generally flat annular rear surface 42 which seats against the die segment shoulder 24 adjacent the outer cylindrical surface 36 of the die.

The die segments 12 are supported for individual and collective radial shifting movement thereof between front and rear support plates 44 and 46, respectively, which have spaced, opposed, parallel plate surfaces 48 and 50 between which the segments 12 are located. The support plate surfaces 48 and 50 are spaced apart slightly more than the thickness of the segments 12 between their front and rear surfaces 14 and 16, respectively, by means of a series of spacer blocks 52 interposed between the plates 44 and 46 in regularly spaced arrangements about the periphery of the die holder radially outwardly of the segments 12 and spring loops 28. Each of the spacer blocks 52 has pins 54 projecting outwardly therefrom which extend into holes 56 in support plates 44 and 46, whereby the plates 44 and 46 and the spacer blocks 52 are maintained in proper alignment. Suitable fastener means (not shown in FIGS. 1 to 4) may be employed to secure the support plates 44 and 46, spacer blocks 52 and die holder segments 12 in axially stacked relationship as illustrated in FIG. 1.

The support plates 44 and 46 have respective apertures 58 and 60 extending axially therethrough, the apertures 58 and 60 being substantially larger in diameter than the initial ID of the die ring 34 so as to allow the unobstructed passage therethrough of a tube or other elongated member that is being drawn through the die ring 34. In a typical tube drawing operation, as for example in tube sinking, a tube will be drawn from left to right as viewed in FIG. 1 through the die 34, and as the tube passes through the die 34 it will be reduced substantially in diameter. Accordingly, the diameter of aperture 58 in the front plate 44 is somewhat larger than the diameter of aperture 60 in the rear plate 46.

The support plates 44 and 46 each have an annular array of regularly spaced, radially directed ball-receiving grooves in their respective opposed surfaces 48 and 50. The number of these radial grooves 62 in each of the plate surfaces 48 and 50 is equal to the number of wedge-shaped die holder segments 12. Thus, for example, if there are three of the die holder segments 12, there will likewise be three of the regularly spaced, radially directed grooves 62 in each of the plate surfaces 48 and 58. Similarly, as illustrated in FIGS. 1 to 4 of the drawings, where there are sixteen of the segments 12, then there will likewise be sixteen of the regularly spaced, radially directed grooves 62 in each of the plate surfaces 48 and 50. The support plates 44 and 46 are rotationally oriented so that each of the grooves 62 in one plate will be aligned with a corresponding groove 62 in the other plate; i.e., such corresponding grooves will lie in a common plane extending through the axis of the holder.

A ball bearing 64 is seated in each of the ball recesses 30 and 32 in each die segment 12, and these ball bearings 64 ride in the radial grooves 62 in the plate surfaces 44 and 46 as best illustrated in FIG. 1. Thus, each of the wedge-shaped segments 12 is supported for freely floating radial shifting movement on four ball bearings 64 as best shown in FIG. 1. By this means the die ring 34 is allowed to automatically seek and maintain correct alignment with the workpiece so that it will apply substantially uniform constrictive force to the workpiece about its annulus, and a predetermined amount of constrictive force is added to the constrictive force of the die ring 34 itself by the force of spring loop 28 applied to the die ring 34 through the wedge-shaped segments 12. If the die ring 34 is intended to vary in diameter during the drawing operation, as for example where a tube is being drawn against a tapered mandrel, then the holder segments 12 will shift radially outwardly to accommodate such enlargement of the die ring 34, and such radial outward shifting of the segments 12 will not be opposed by any substantial friction, but only by the constraining force of the spring loop 28. Similarly, since the segments 12 expand outwardly with the die ring 34, there will be no substantial opposing friction from engagement of the die ring 34 against the seat shoulder 24 in the segments. Accordingly, there are no substantial variable or undeterminable frictional forces opposing the expansion of the die ring 34, and all of the forces are predictable.

In normal tube drawing operations the OD of the die ring 34 will not expand more than about 50% from its initial, minimum size as illustrated in FIG. 1, and that amount of expansion will result in separation between the side surfaces 18 of the segments 12 which is barely perceptible, and accordingly the OD of the die ring 34 remains substantially fully confined within the inner surface portion 20 of the segments 12 and substantially fully supported by the shoulder 24 against axial displacement.

The freely floating support arrangement for the wedge shaped segments 12 allows the segments 12 to shift radially outwardly different relative amounts to accommodate variations from round of the cross-sectional shape of the tube or other elongated structure being drawn. For example, where a tube is drawn over a mandrel having a cross-section that is oblong, hexagonal, square or of other out-of-round configuration, the die ring 34 will be permitted to follow such odd cross-sectional configuration while nevertheless being fully peripherally supported by the inner ends of the segments 12, since the segments are allowed to freely shift radially relative to each other to accommodate such odd configurations.

The combination of support plates 44 and 46, ball bearing supported holder segments 12, spacer blocks 52 and die ring 34 is normally supported on a drawbench in a suitable support body or block 66 having a forwardly facing surface 68 against which the rear support plate 46 seats, and having an axial passage 70 therethough into which the tubular projection or boss 72 on the rear support plate 46 seats.

While ball bearings 64 have been shown and described as being seated in ball recesses in the segments 12 and arranged to ride in grooves 62 in the plate surfaces, it is to be understood that alternatively the balls may be seated in similar recesses in the plate surfaces so as to ride in similar radially oriented grooves in the fiat front and rear surfaces of the die segments. While it is preferred to utilize ball bearing guide means to control the radial orientation of the segments 12 while allowing them to shift in the radial direction, it is to be understood that alternatively other guide means may be employed for the same purpose, as for example tongue-and-groove means engageable between the holder segments and holder plates or pin-and-groove means engageable between the holder segments and plates. Additionally, although it is preferred to have such guide means engageable between both the front and rear surfaces 14 and 16 of each segment and the respective support plates 44 and 46 so as to obtain optimum stability of the segments 12, nevertheless if desired the ball bearing or other guide means may be provided so as to be operatively engageable between only one surface 14 or 16 of each segment 12 and the corresponding support plate 44 or 46 without departing from the invention.

Referring now to FIGS. and 6 of the drawings, a second form a of the invention is shown in these figures wherein the annular array of wedge-shaped segments12a is peripherally encased within an annular housing 74' which serves the function of the spacer blocks 52 shown in FIGS. 1 and 2, separating the support plates sufliciently for freedom of radial shifting movement of the segments 12a, and which aditionally serves to house a flexible inner tube 76 composed of neoprene or other suitable elastomeric material which is coupled through a suitable conduit 78 to an adjustable fluid pressure source 80 diagrammatically shown in FIG. 5. The adjustable pressure source 80 may furnish any suitable pressurizing fluid, either liquid or gas, i.e., either hydraulic or pneumatic, according to the requirements of any particular drawing operation. Thus, where relatively low pressure is all that is required, a pneumatic pressure source will be suitable; while a hydraulic fluid pressure source will be required if high pressures are desired.

The housing 74 defines an inwardly facing annular groove 82 of rounded cross-section within which the radially outwardly facing half of the inner tube 76- seats;

while the radially inwardly facing part of inner tube 76 7 seats in an opposed, radially outwardly facing annular channel 84 of rounded cross-section. In order to keep the inner tube 76 fully enclosed within the housing 74 despite radial contraction and expansion of the annular array of wedge-shaped segments 12 corresponding to pressure changes within the inner tube 76, the housing'74 is provided with a pair of parallel, radially inwardly directed annular ribs 86 which extend into a pair of complementary grooves 88 in the outer ends of the segments 12a. The complementary housing ribs 86 and segment grooves 88 are of sufficient depth to remain interengaged over the entire range of radial shifting movement of the segments 12a, so that the inner tube 76 will at all times be fully confined between the housing and the segments as best illustrated in FIG. 5.

A valve 90 is disposed in fluid conduit 78 for selectively admitting fluid pressure through the line 78 into the inner tube 76 or relieving fluid pressure from inner tube 76 through line 78 and thence out through bleeder line 92 which may have a bleeder valve 94 therein for adjusting the rate of bleed-oif from the inner tube 76. This combination of an adjustable fluid pressure source and valve means to permit bleed-off at any desired rate allows full operator control of the pressure applied to the inner tube 76 and hence of the radially inwardly directed force of the holder segments 12a against the die ring 34a, thereby allowing operator control over the effective Working strength of the die ring relative to the workpiece. At the same time, the flexible nature of the inner tube 76 with either liquid or gas under pressure therein, allows the desired self-aligning action of the die segments.

By employing a pneumatic or gaseous pressure source, the net effect of the radially inwardly directed force of the inner tube 76 on the die segments 12a will be that of an adjustable biasing force, or an adjustable spring, since the gas under pressure is resilient. On the other hand, if a hydraulic or liquid fluid pressure source is employed, then the general effect will be of a substantially nonresilient or generally rigid inward force applied to the segments, but nevertheless a force which will be equalized over the entire annular array of holder segments 12w so that there will be a measure of resiliency as between the respective segments.

In the embodiment of the invention shown in FIGS. 5 and 6, the fastener means for securing the die holder together is shown in the form of a plurality of bolts 96 which extend through the front support plate 44a, housing 74, rear support plate 46a and into support body 66a, at spaced intervals around the periphery of the apparatus.

It will be noted in FIG. 5 that the inner surface 20a presented by the annular array of holder segments 12a is a straight cylindrical surface of non-stepped configuration. In this case, the die ring 34a is radially encompassed by this cylindrical surface 20a, and the die seat is provided by the flat forward end surface 98 of a die ejector tube 100 which extends from the rear through the openings 70a and 22a in the support body 66a and the rear support 46a, respectively. While this die ejector tube 100 has the advantage of providing a convenient means for ejecting the deformed die 34a after the latter has been expanded during a tube drawing operation such as a tapering operation, it has the disadvantage of presenting a fixed seat against which the die 34a expands, thereby introducing a friction factor to the overall operation that is not present when the stepped die holders 12 of FIGS. 1 to 4 are employed. However, it will be apparent that the stepped die holder like that best shown in FIGS. 1 and 4 may be employed in the general type of die holder apparatus of FIGS. 5 and 6 wherein the inner tube is employed, or that the ejector type of die holder may be employed in the spring biased type of holder mechanism shown in FIGS. 1 to 4, without departing from the invention. Similarly, although the other forms of the invention shown in FIGS. 6 through 12 and hereinafter described are illustrated with die holder segments having the stepped configurations, it is to be understood that the ejector-type arrangement of FIG. 5 may be alternatively employed in these other configurations.

Although the inner tube housing 74 of FIGS. 5 and 6 is of annular configuration when assembled, it may be provided in two or more segments to facilitate assembly of the apparatus.

Referring now to FIGS. 7 and 8 of the drawings, these figures illustrate a third form 10b of the invention which is similar in construction to the first form 10 shown in FIGS. 1 through 4, except for the fact that the die holder segments 12b are each individually biased radially inwardly by a separate coil compression spring 28b which is supported for adjustable compression on a respective jack screw 102. The jack screws 102 are threadedly engaged through the respective spacer blocks 52a, and each have torqueing means such as a screwdriver-receiving slot 104 exposed on the outside of the die holder 10b for radial adjustment of the jack screw 102 and consequent adjustment of the compressive force of the respective spring 28b radially inwardly against the respective holder segment 12b. The springs 28b are each compressed between a flange 106 on the respective jack screw 102 and the outer end of the respective holder segment 12b. The inner end portion 108 of each jack screw 102 is slidably engaged within an axial recess 110 in the outer end of the respective segment 12b to retain the jack screw 102 and compression spring 28b properly radially oriented relative to the respective holder segment 12b.

The jack screw type of adjustment provided in the third form of the invention illustrated in FIGS. 7 and 8 allows selective individual adjustment of the supporting force of each die holder segment 12b against the periphery of the die 20 to accommodate drawing operations wherein the elongated structure being drawn will vary from round. On the other hand, the jack screws can be collectively adjusted to all apply substantially the same radially inwardly directed force against their respective die holder segments 12b so as to apply a uniform peripheral force against the die 20, and such inward force can be adjusted by adjustment of all of the jack screws the same amount.

Despite the aforesaid individual or collective adjustment of the jack screws 102, by applying the adjustable forces on the segments 12b through compression springs 2811 the die holder will have a self-centering action similar to that of the first form of the invention shown in FIGS. 1 to 4 and the second form of the invention shown in FIGS. 5 and 6.

FIGS. 9 and illustrate a fourth form of the invention which is similar to the third form shown in FIGS. 7 and 8 in that the die holder segments 120 may be individually adjusted for application of varying inward forces upon the die 20c, but which differs from the third form of FIGS. 7 and 8 by employing fluid pressure actuation means instead of strictly mechanical means for applying the radially inwardly directed forces to the die holder segments 12c.

Thus, in the fourth form 100 shown in FIGS. 9 and 10, the die holder segments 12c are ball-bearing supported for floating radial movement between front and rear support plates 44c and 46c, respectively, and instead of employing spacer blocks, the rear support plate 460 has an integral, forwardly directed cylindrical peripheral flange 112 thereon. Each of the die holder segments 120 is provided with an individual fluid pressure actuated cylinder 114 which is supported on the outside of flange 112 and has a plunger 116 which projects radially inwardly through a respective hole 118 in flange 112 and has a rounded inner end which seats in a complementary rounded cup 120 in the outer end of the respective die holder segment 12c.

Single-acting cylinders 114 will normally be sufficient for the present purpose, and each of the cylinders 114 is supplied with fluid under pressure through a respective individual supply conduit 122, these supply conduits 122 each communicating with a common selector manifold 124 through a respective valve 126 which in one position will allow fluid pressure from the selector manifold 124 to pass through conduit 122 to the respective cylinder 114, and in its other position will allow bleed-off of fluid pressure from the respective cylinder 114 through conduit 122 and thence out through bleeder line 128 and bleed control valve 130.

The selector manifold 124 is supplied with fluid under pressure from an adjustable fluid pressure source 132, and the selector manifold is operable to supply fluid pressure collectively to all of the cylinders 114, or selectively to any number of the cylinders 114.

The fluid pressure can be collectively relieved from the cylinders 114 through selector manifold bleeder line 134 as controlled by bleed control valve 136 therein.

It will thus be seen that the fourth form of the invention illustrated in FIGS. 9 and 10 of the drawings is similar to the second form shown in FIGS. 5 and 6 in that both of these forms provide for collective fluid pressure control of the radially inwardly directed forces of the die holder segments against the die, which control allows for self-centering of the die relative to the workpiece. The fourth form of FIGS. 9 and 10 is likewise similar to the second form of FIGS. 5 and 6 in that when the fluid pressure is gaseous or pneumatic the holder segments are resiliently biased against the die ring, whereas with liquid or hydraulic fluid pressure which is substantially incompressible the die segments are more rigidly held in position, although collectively shiftable for self-alignment.

However, the fourth form of FIGS. 9 and 10, by employing individual fluid pressure actuated cylinders 114, permits selective individual control of the radially inwardly directed forces of the respective die holder segments against the die, which cannot be achieved in the second form of the invention shown in FIGS. 5 and 6.

In FIGS. 9 and 10 the die holder apparatus has been illustrated in an expanded condition wherein the die holder segments 120 have been shifted radially outwardly from their innermost positions illustrated in phantom lines to outer positions illustrated in full lines as a result of drawing a tube 138 over a tapered mandrel 140 so as to give the tube 138 a tapered configuration. The solid die holder segments are still quite closely spaced, with very little clearance therebetween, so that they still substantially completely circumscribe the die ring and provide substantially complete circumferential support to the solid die ring therein.

FIGS. 11 and 12 illustrate a fifth form of the invention which is the same in all respects as the first form shown in FIGS. 1 to 4 except for the addition of a series of brake pads 142 mounted in complementary recesses 144- in the front support plate 44d. One brake pad 142 is provided for each of the die holder segments 12, the brake pads 142 being frictionally engageable against the front surfaces 14 of the respective segments 12 so as to resist expansion of the die holder segments. The magnitude of this frictional force on each die holder segment 12, which in turn results in a radially inwardly directed constricting force on the die ring 34, is adjustable by means of an adjusting screw 146 engaged in a threaded bore 148 extending through the front support plate 44d.

It will be apparent that appropriate manipulation of the adjusting screws 146 will permit either individual or collective adjustment of the radially inwardly directed constricting force of the die holder segments 12 on the solid ring 34.

While the instant invention has been shown and described herein in what are conceived to be the most practical and preferred embodiments, it is recognized that departures may be made therefrom within the scope of the invention, which is therefore not to be limited to the details disclosed herein, but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices.

I claim:

1. Apparatus for holding a drawing die ring which comprises an annular array of at least three generally wedge-shaped segments which define generally radially inwardly directed surface means peripherally engageable about the drawing ring to support the ring generally 00- axially between the segments, said segments being radially shiftable between a contracted position and an expanded position, and force-applying means engageable with said segments opposing movement of the segments from said contracted position toward said expanded position.

2. Apparatus as defined in claim 1, which includes a pair of spaced, opposed, generally flat support surfaces arranged generally normal to the axis of said annular array of segments between which said segments are disposed, said surfaces at least partially confining the segments in the axial direction and being spaced apart slightly more than the axial thickness of the segments to permit free sliding movement of the segments in the radial direction.

3. Apparatus as defined in claim 2, Which includes guide means engageable between each of said segments and at least one of said support surfaces, said guide means maintaining said segments generally radially oriented and guiding the segments in their shifting movement in generally radial paths.

4. Apparatus as defined in claim 3, wherein said guide means includes ball bearing means engageable between both of said support surfaces and each of said segments.

5. Apparatus as defined in claim 1, wherein said inwardly directed surface means defined by said segments is of stepped configuration, presenting an axially facing shoulder against which said die ring seats during a drawing operation.

6. Apparatus as defined in claim 1, wherein said forceapplying means comprises spring means peripherally en- 1 1 gaged with each of said segments so as to bias the segments radially inwardly toward said contracted position.

7. Apparatus as defined in claim 6, wherein said spring means comprises a tension spring loop peripherally engaged about said annular array of segments.

8. Apparatus as defined in claim 6, wherein said spring means comprises a separate spring member peripherally engaged against each of said segments, and adjustable support means for each of said springs permitting independent adjustment of the radially inwardly directed force of each spring against its respective segment.

9. Apparatus as defined in claim 1, wherein said forceapplying means comprises fluid pressure actuated means peripherally engaged with each of said segments and selectively operable to apply radially inwardly directed force to said segments.

10. Apparatus as defined in claim 9, wherein said fluid pressure actuated means comprises housing means peripherally arranged about said annular array of segments, flexible inner tube means peripherally disposed about said annular array of segments within said housing, and means connected to said inner tube means for introducing fluid pressure therein.

11. Apparatus as defined in claim 9, wherein said fluid pressure actuated means comprises a separate fluid pressure responsive device peripherally engaged against each of said segments, and fluid pressure supply means connected to each of said fluid pressure responsive devices for selectively actuating said devices both collectively and independently.-

12. Apparatus as defined in claim 11, wherein said fluid pressure responsive devices are hydraulic cylinders each having a generally radially oriented plunger engageable against a respective segment.

13. Apparatus as defined in claim 1, wherein said forceapplying means comp-rises a separate brake pad member generally axially engageable with each of said segments, and adjustable support means for each of said brake pad members permitting independent adjustment of each brake pad member in the axial direction.

14. Apparatus as defined in claim 1, wherein the summation of the included angles of the wedges is approximately 360, whereby said wedges form a generally closed ring in said contracted position.

15. Apparatus as defined in claim 1, which includes approximately sixteen of said segments.

16. Apparatus as defined in claim 9, wherein said fluid pressure actuated means is hydraulically actuated.

17. Apparatus as defined in claim 9, wherein said fluid pressure actuated means is pneumatically actuated.

18. Apparatus as defined in claim 1, wherein said annular array of segments has front and rear sides in the axial direction, said apparatus including support means on at least said rear side of the segments and having a passage therethrough arranged generally coaxially of the segments, and an ejector tube slidably mounted in said passage and having a front end defining an axially facing annular shoulder, said ejector tube being slidable between a retracted drawing position wherein said shoulder is proximate said rear side of the segments and serves as a seat against which said die ring abuts during a drawing operation, and an extended ejection position wherein said shoulder is shifted forwardly at least part way through said inwardly directed surface means defined between the segments so as to eject the die ring forwardly from between the segments upon completion of a drawing operation.

References Cited UNITED STATES PATENTS 712,974 11/1902 Smith 72465 1,735,850 11/1929 Boedeker 72285 2,294,13 8 8/ 1942 Strocl; 72467 2,413,595 12/1946 Wiser 72468 3,213,663 10/1965 Coan 72468 3,327,513 6/1967 Hinshaw 72274 FOREIGN PATENTS 1,131,174 6/1962 Germany.

LOYELL A. LARSON, Primary Examiner US Cl. X.R. 

